Resistance unit



Nov. 19, 1935. F. w. McDONELL w 2,021,486

RESISTANCE UNIT Filed Feb. 16, 1934 anmummuumi anmnnun INVENTOR a amid/ 2 ATTORNEY Patented Nov. 19, 1935 PATENT OFFiCE 2,021,486 RESISTANCE UNIT Frank W. McDonell, Fairlawn, N. J., assignor to Ha'rdwiek, Hindle, Inc., Newark, N. J.

Application February 16, 1934, Serial No. 711,505 3 Claims. (01. 201-61) This invention relates to a special form of resistance unit and has for one of its objects the provision of a resistance unit that combines cheapness, durability and emciency; that is to say, a resistance unit which can be cheaply made, yet one that will stand a large amount of abuse and one that is highly efficient in operation, which includes a unit having heat-radiating surfaces of considerable extent.

- Another object of my invention is to provide a resistance unit that may be readily mounted for operation.

These and other objects will appear to one familiar with resistance devices of the character described, after reading the specification taken in connection with the drawing, wherein:

Figure l is a perspective view of the frame member for carrying the resistance winding per se.

Figure 2 is a plan view of the frame with the resistance winding installed in place within the frame.

Figure 3 is a view similar to Figure 2 but with the device completed and ready for use.

Figure 4 is an enlarged section on the line 44 of Figure 3.

In the various views, I is a frame member having upturned sides 2 and 3 thereby forming a channel. I preferably make the channel-shaped frame member I from suitable metal in order to give rigidity and strength to the complete unit. By making the frame member in the form of a channel, I can use relatively thin metal, particularly when the metal is of steel. Near each end of the web or flat bottom portion of the frame, there is punched or formed upwardly between the side members 2 and 3, a dam or stop member 4, leaving a cross-opening 5 in the bottom I, and having a width substantially the same as the height of the sides 2 and 3. The ends of each stop member 4 are preferably on a line with the inner edges of the sides 2 and 3 so as to act as braces for these sides, as well as stops for the material going into the channel between these stops as will be later pointed out.

In addition, each of the stop members I has a finger or projection 6 simultaneously punched out of the bottom portion I, leaving a slot 1.

After the frame member has been made substantially as shown in Figure 1, it is ready to receive a resistance winding 8 wound on a suitable,heat-resisting form 9 which may be a strip of mica. The ends of the winding are fastened to terminals in any satisfactory manner, that shown comprising an L-shaped terminal l0 preferably of good conducting material such as copper. The 'two end terminals may have one arm of the terminal resting on the ends of the form or actually resting on one or more turns of the winding 8, and they are held in place by eyelets H which pass through the form 9 carrying the winding.

Connection of the winding to the terminal may be made by taking one or more turns around the eyelet before it is spun or swedged over into 10 terminal-holding position. If desired, additional terminals may be positioned intermediate the end terminals, one such terminal being indicated -in Figures 2 and 3.

After the formwith the winding and terminals thereon has been completed, itis placed in position within the sides 2 and 3 and between the stops 4, it being understood that a suitable insulator l2, such as mica, is first placed in the bottom of the channel frame member. After this is done, small insulators i3 and ll of suitable material, such as mica, are placed above they terminaland eyelets ii at the ends, and the fingers 6 are then bent over into position to clamp the form and winding to hold it in its initial assembled position ready to receive a covering l5 preferably of vitreous enamel, which may be inserted in any satisfactory manner into the channel frame between the dams or stops 4.

I prefer to submerge the entire unit in vitreous enamel sl-ip, holding it in an upright position during submersion, so that on removal the slip will not only adhere to all the external sides of the frame, but a much greater amount will be retained in the frame member by the stops 4, and the side walls 2 and 3. The enamel may be applied in some other way, as by spraying. In the dipping operation the unit may be held by the holes in the extremities of the terminals l0. n the ends of the terminals It should be 'covered by enamel, they are wiped cleanbefore the next operation.

The unit is then placed in a furnace, still in an upright position, and heated until the vitreous enamel slip is fused. As the slip fuses, the side members 2 and 3 and the stops 4 prevent the slip from flowing out of the frame member, so that when cooled and, removed from the furnace, the winding 8 is completely sealed in vitreous enamel 0 'within the frame, and the enamel is intimately bonded to the frame, thus producing a resistor which is practicallymoistureproof. In addition, the frame member is completely covered by vitreous enamel which makes it also impervious to moisture as well as contributing to its good appearance.

After the unit has been thus completed, it is ready for use and may be mounted through the medium of the slots 1 provided in the ends of the frame in the manner already described.

The form of the frame is such that the unit may be handled with impunity, and the winding being placed relatively close tothe bottom of the frame provides a considerable area for the dissipation of the heat generated by the winding.

What I claim is: l

l. A resistance unit including a nombreakable, non-bendable, heat-resisting, channelshaped frame member having stops punched upwardly from the bottom of the frame, but inwardly spaced from the opposite ends of the channel between the sides thereof, leaving openings in the bottom for the purpose described, a winding on a heat-resisting form positioned in but insulated from'the channel member and between said stops, said stops having bendable portions for initially holding the winding in position in the frame, the channel carrying a covering of vitreous enamel over the winding and terminals for the winding extending through said covering.

tute means by which the unit may be mounted 5 for use.

3.- A resistance unit including a metal frame of relatively thin material having a flat bottom portion with upturned sides, combined stop and holding parts punched upwardly from the bottom 10 portion spaced from but near the opposite ends thereof leaving openings in said bottom portion, the stops parts being in width substantially the same as said sides and extending all the way from one side to the other, a winding on a heat-resist- 1! ing form located between said stops but insulated from the frame and initially held in place in the frame by said holding parts which are bent over to engage the winding form but out of contact with said winding,-a covering of vitreous enamel over :0 the frame and winding and substantially filling the channel between said stops, and terminals for the winding extending through the covering and be! yond the sides of the channel.

. I FRANK W. McDONELL. 

